1. Field of the Invention
This invention is a process for converting calcium phenylpyruvate to sodium phenylpyruvate.
L-phenylalanine is a major component in the popular low calorie sweetener aspartame, formally known as L-aspartyl-L-phenylalanine methyl ester. Whereas this is by far the most important and valuable use of this amino acid, it has other minor applications in pharmaceuticals and animal feed supplements. One route to the synthesis of L-phenylalanine involves the production of phenylpyruvic acid as an intermediate. The phenylpyruvic acid is then converted to sodium phenylpyruvate which is then subjected to a transamination reaction with aspartic acid to produce L-phenylalanine.
U.S. Pat. Nos. 4,152,352, 4,351,952 and 4,447,644 disclose a process for the production of an arylpyruvic acid by the carbonylation of aryl alkyl chloride with carbon monoxide, in the presence of an inorganic base and a metal carbonyl compound. A calcium salt of an arylpyruvic acid is produced as an intermediate and is converted to arylpyruvic acid by acidification with HCl and extrattion with ether. Acidification and ether extraction suffer from the following disadvantages. The use of HCl and ether add raw material costs to the process. In addition, because large amounts of ether are required, moving the ether through the reaction system is costly, and the loss of ether represents a pollution hazard.
U.S. Pat. No. 4,518,800 describes a process for preparing crystallized monohydrated sodium phenylpyruvate from benzaldehyde in the presence of ethanolamine and hydantoin.
U.S. Pat. No. 4,621,153 describes a process for obtaining amino acids, e.g. phenylalanine from a fermentation broth. The process involves providing a source of Ca.sup.++ ions sufficient to precipitate a Ca.sup.++ amino acid complex, separating the precipitate, dissolving the precipitate at a pH below 8.5 and recovering phenylalanine.
U.S. Pat. No. 4,152,352 also discloses a process for the production of arylpyruvic acids which comprises reacting an arylmethylhalide in a liquid solvent medium with carbon monoxide at pressures of 5-200 bazs in the presence of a catalytic amount of a metal carbonyl compound such as ion, cobalt or nickel and an alkaline earth metal inorganic base.
U.S. Pat. No. 3,215,620 describes a process for removing anionic surfactants from aqueous solutions, using an ion exchange technique.
The present invention provides a process for converting calcium phenylpyruvate to sodium phenylpyruvate in high yield and purity without the eeed for organic solvent extraction which is then suitable for subsequent reaction with aspartic acid to produce L-phenylalanine.